Velocity modulation tubes



DCC. 4, P. VOGE VELOCITY MODULATION TUBES Filed Feb. 17, 195v 4Smeets-Sheet 1 JEH/V P. V065 BY 63W@ www@ Wma/9m Mgg@ ATTORNEY Dec. 4,1956 J. P. voGE VELOCITY MouULATIoN TUBES 4 Sneeuw-Sheet 2 Filed Feb.17, 1951 lNvENToR JfA/V f? V065 BY di, WM Mw?,- T

ATTORNEY? Dec. 4, 1956 J. P. voGE 2,773,214

VELOCITY MODULATION TUBES Filed Feb. 17, 1951 4 Sheets-Shes*b 3 ATTORNEYDec. 4, 1956 J. P. voGE VELOCITY MODULATION TUBES Filed Feb. 17, 1951 4Sheets-Sheet 4 INVENTOR Jf/V E VOGE BY Q7 l QM WM, @am @l /f ATTORNE 5United States Patent O VELOCITY MODULATION TUBES Jean P. Voge, Paris,France Application February 17, 1951, Serial No. 211,506 9 claims; (ci.315-6) The .present invention rela-tes to electron discharge 'tubes ofthe velocity modulation type, and more particularly to a novel form ofklystron tube having a wide band of frequencies over which it can betuned without alteration of the geometrical shape of its resonantcavities.

This application is a continuation in part of my copending applicationSerial No. 725,682, filed January 31, 1947, now Patent No. 2,614,234.

The klystron tube of my invention includes two hollow body resonators orresonant cavities of essentially prisma-tic or cylindrical shape (in thebroad geometrical sense of the word cylindrical). The two cavities,termed buncher and catcher in the terminology of the art, function aswave guides Within which systems of standing waves are established byelectromagnetic fields 'which have the same frequency in both, but whichare of different .phase wave lengths Ain the two. The systems oflstanding waves are generated and maintained, at least in the catchercav-ity, by an `electron beam of ribbon shape, i. e., having latwo-dimensional extension, which 'is projected through the two cavitiesacross a gap in each separating electron-permeable areas or grids in twoopposite faces of the cavities. In passing through the cavity, theelectron beam follows trajectories which are perpendicular to the long`dimension of these resonators,

i. e., to the generators or elements of their cylindrical or prismaticsurfaces, with the breadth of the electron beam parallel to suchgenerators or elements. In a preferred embodiment, the breadth of theelectron beam is in both cavities substantially equal to an integral butdifferent 'number of quarters of the phase wave length of the standingWave fields existing in `the cavities.

Prior art devices of the klystron typ-e use reentrant chambers orcavities having three principal shapes: reentrant prismatic, reentrantcylindrical in the form of figures of revolution :about an axisperpendicular to the cavi-ty gaps, and reentrant cylindrical in the formof` figures of revolution about an laxis :from said gaps.

Klystrons of the iirst and second types have pencilshaped beams ofelectrons and klystrons of the third type have centrifugal orcentripetal plane starlike Ishaped beams, i. e., beams emitted -by anaxial :cathode structure and collected by a ring-shaped collector, oremitted by 'an annular cathode element and collected by an axialcollector. In all three types of tube, the ultra-high freparallel to andremote quency `inputto the catcher cavity produces across its gap anelectromagnetic el-d the electric vector of which is directed along theline of ,travel of the electrons. The gap areas of the resonators, i.e., the areas of the portions of opposite faces of the resonators whichapproach each other to form Ithe grids, are so scaled that theelectromagnetic field is near its peak value over the entire area at thegaps and, in particular, has no nodes in the region of the gaps. Inother words, the electron stream traverses the electromagnetic fields ofthe cavities near the location where thestanding wave amplitudes aremaximum and over paths which, las to all `dimensions yof such paths, arevery rn-uch smaller than the phase-wavelength of the oscillations in theresonant cavities.

I have determined by analysis and experiment that by using as cavityresonators prismatic conducting cavities traversed by .a flatribbon-shaped electron 'beam whose width is parallel to the generatorsof the cylindrical surfaces to which the cavities conform, the beamhaving in a preferred form substantially the sam-e width as the heightIof the cavities, and by dimensioning the cavities in s-uch a way thatthe buncher cavity oscillates over an even number Iof quarter phasewavelengths in the direction parallel to these generators and bydimensioning the catcher cavity so that it oscillates over an odd numberof quarter phase wavelengths, the bandwidth lcan be substantiallyincreased.

.It is therefore a major object of my invention to provide an ultra-highfrequency electron discharge device of the velocity lmodulated electronbeam type having novel internal proportions and having unusual bandwidthcharacteristics.

A further object of my invention is to produce lan electron velocitymodulated tube of large bandwidth without the necessity of corrugatedflexible lor otherwise d-eformable walls for the cavity resonators.

A further object of my :invention is to provide a novel ultra-'highfrequency device of the velocity modulation type wherein a ribbon-shapedelectron beam of twodimensional extension is projected transverselythrough substantially the total height of the hollow prism'aticresonator means.

A further object of my invention is to provide a prismatic reentrantbuncher cavity reson-ating on an even multiple of quarter-wavelengthsand :a prismat-ic reentrant catcher cavity of substantially th-e sameheight as the buncher and resonating on an lod-d multi-ple ofquarterwavelength, both chambers being traversedby 4a wide ribbon-shapedelectron beam over their height.

The foregoing and other objects of my invent-ion will be best understoodfrom the following description of a preferred embodimentthereofreference being had to the accompanying drawings wherein likenumerals of reference indicate Isimilar parts throughout the severalviews and in which:

Fig. l is a schematic view of ,a klystron tube intended to illustratecertain theoretic-al considerations on which the -invention is based;

Figs. 2 and 3 are respectively a vertical longitudinal section and ahorizontal cross-section of an electron velocity modulation tubeembodying my invention, Fig. 3 being taken on line 3-J3 of Fig. 2 andFig. 2 being taken on the line 2 2 of Fig. 3;'

Figs. 4 and 5 are respectively perspective views of the bu'ncher andcatcher cavities of the klystron of Figs. 2 and 3; and l Fig. 6 is adiagram for the'calculation of the cross sectional dimensions of thecavities in klystrons ac-cording to my invention.

Referring to Fig. 1 which is idealized, and using the no-tation ofArthur E. Harrison, Klystron Tubes, Mc- Graw-Hill, 1947, theinstantaneous voltage across the input gap 1 between grids lland 12 ofthe buncher cavity is:

E=E1 sin wifi 'i2=2111(x) sin @1oz-10) where I0 is the number `ofelectrons entering the cavities parameter, z2 the time of arrival in theoutput -gap for an electron leaving the input gap at time ti, and To thetransit time from buncher to catcher for an electron with averagevelocity. Maximum current i2 occurs when the bunching parameter has avalue of 1.84.

Let Rs be the shunt resistance .of the catcher `resonator and C thecapacity between its grids 4 and 5, spaced d centimeters apart. Then,

:0.088'10-12 farads l) where A is the area of the grids .in squarecentimeters (perpendicular to the plane of Fig. 1). The Q of cavity 2will then 'be vgiven by and the output voltage by:

EFRaFf-.a on

For a given amplification factor (i. e. a given Ez) and for i2 maximum(bunching parameter equal to 1.84) and i a given angular frequency w1,the Q factor will be proportional to C as shown by Equation (.3).

The invention is concerned with increasing the bandwidth of the tube. Tothis end it would be desirable to reduce Q by reducing C. Equation (1)implies that this can be achieved by reducing A or by increasing d.Neither of these solutions is desirable, however, because a reduction ofA reduces the intensity lo of the beam and hence the intensity of i2,while increasing d introduces perturbations into the operation of thetube in View of the ei'iect of transit time between the grids 4 and 5.

`instead, Vlet the grids f and 5 be considered as forming the twoconductors of a transmission line of length L2 transverse to the`direction of propagation of the beam and supporting a system ofstanding waves. The line will have a characteristic impedance Ze Yand isshortcircuited at its end 6. The impedance of the line at the endopposite the short circuit is Here ,82 is the phase constant in thegeometric propagation constant of the line. See Principles of Radar,

one obtains RS=QZ tan/8212. l For a given Rs, Q may be reduced byselecting 6212 as nearly to as desired. According tothe presentinvention one chooses for the catcher a mode of vibration such that thelength of the cavity traversed by the beamis equal to an odd number ofquarter phase wavelengths, i. e., so that `flzlz is equal vto K being aninteger.

According to a further feature of the invention the output coupling loopis located close to the Open-circuited end of the grids 4 and S and thecatcher cavity is closed oil at this end by a rounded chamber of lowheight, i. e. of low extension along the length of the generators of themain catcher cavity cylinder or prism.

It is known that Ithe ybunching parameter is proportional both to thedrift distance and -to the peak value ot the input modulation voltage(voltage across the gap of the buncher cavity). In order to have a peakvalue of E1 in the buncher cavity substantially higher than the peakvalue of the voltage in the input line which is coupled to the bunchercavity, one chooses for the buncher cavity a `Inode of oscillation suchthat the height Vor length of this cavity which is traversed by thewidth of the electron beam is equal to an even number of quarter phasewavelengths, and the input line coupling loop is located at a node ofthe oscillations, i. e. either close to the bottom wall or to t-he topwall of the buncher, which is closed at both ends by a conducting plateor wall. In this way E1 can be increased, permitting -a reduction in thedrift distance without changing the bunching parameter.

In Fig. l, there is shown at 7 a wide, tlat, ribbonshaped electron beamhaving a width equal to the cornmon heights l1 and l2 of the grids ofthe cavities il and 2 and of very small extension in the directionperpendicular to the plane vof the igure. 8 `represents the standingwavepattern of the electric iireld in the buncher Acavity as a half wavewith nodes at the short-eircuited terminals 9 and i@ of the grids lliandiZ. i3 represents the standing wave pattern of the electric tield inthe catcher cavity `as aV quarter wave with a node at theshort-circui'tedterminal 6 of grids 4 ant 5 and with an anti-node at theopen circuited end of these grids.

The input coupling loop Mi is located close to anode Of ,the sinusoidalstanding wave pattern 3 and the output coupling loop 15 is located closeto the maximum amplitude or the sinusoidal standing wave pattern 13. `ltis to be borne in mind, of course, that the dimensions of the grids aresmall in directions perpendicular 'to 'the plane of the iigure.

Referring now to Figs. 2 and 3, 2 l represents a vacuum tight envelopeof some Asuitable material such as glass'. inside the envelope ls anelectrode assembly 202 supported by a pair of standards 293 which aresealed through the wall of envelope Ztland constitute lead-in conductorsto the cavity resonators for connecting them to a suitableunidirectional source of potenti-al 204, shown as a battery.

The electrode .structure 2&2 comprises a cathode. heater 205 which mayfor example be in the form of a helix fed from local source 2% throughone pair of lead-in wires 207.

A long Hat-shaped cathode has its exterior face (Fig. 3) coated with amixture of barium .and strontium or of other suitable thermionicallyemissive material. Cathode 263 is supported between insulating spaces269 and 2l@ and is connected to lead-.in conductor 211.

i2 is a line-focussing and accelerating electrode cone Vnected tolead-in conduct-or li; and thence to a suitable voltage positive withrespect to the cathode, supplied for example by a tap `on the battery264 as shown.

To the right .of the collector Ztl/ the glass tube envelope is replacedlby a metallic membrane 2&6 sealed to the glass and provided with coolingtins 2K7.

The buncher and catcher resonators 218 and 219 are of, rectangularreentrant cross section. These cavities are bounded by a common thickmetal bottom wall 220, outer smania.

lateral walls 221 .and 222, a common .separative wall 223, `front wall224 and rear wall 225 and by walls 227 and 228. Walls 224, 223 and 22Sare provided with flat rec tangular slots extending, in the embodimentshown, over the total height of the cavities and aligned lineally with peach other and with cathode 298 and collector 214. The

p with cathode and collector. This corridor and cavity 218 are furtherbounded by common top-wall 229.

The cavity 219 is extended in an upward direction, i. e.

in the direction of the generators, by means of a cavity of rectangularcross-section 230. `The cavity 230 is Without nreentnant portion and isof low height or short extension `in the direction of the prismaticelements. The cross-sectional dimensions of the cavity 230 are largerthan those of the cavity 219 and it is closed at the top by means of atop wall 231. The transition between the lateral walls of cavity 219 andthe lateral walls of the cavity 230 is effected by means of a roundedportion 232 best seen in Fig.

All the walls bounding the cavity resonators are of copper or some `goodelectrically conducting material ormay be plated with a good conductingmaterial. y

p Upper and lower insulating spacers 269 and 210 surround the cavityassembly `and are affixed to `the top and bottom walls 229 and 220 byscrews 237.

On either side of the rectangular slots in the walls 224 and 225,` andat either side of the ends of the field-free drift space corridorbounded by plates 227 and 22S, there are provided vertical rod-likesupports 23S of small diameter supported parallel to the generators ofthe prismatic cylindrical cavity v-olumes. Fine wires are wound `onthese rods to form grids 233 and 234 for the buncher and 235 and 236 forthe catcher. All four grids are therefore of substantially flatrectangular shape and have the same shape .and area as the cathode208and collector 214. i

Input loop 239 extends through an opening in cavity 218 and is locatednear its top-wall 229. One of the ends of the loop is connected to theinner side of wall 221 of cavity 218.

`Output loop 240 extends through an opening in cavity 219 and is locatedat the non-short-circuited portion of grids 235 and 236, i. e. adjacentthe beginning of flared wall portion 232. Loop 240 has one end connectedto the inner side of wall 221 of cavity 219.

`Loops 239 and 240 are provided with conducting extensions 241 and 242,which are surrounded by tubular conductors 243 and 244, the inner endsof which are fastened to the outer side of wall 221 around the openingsthrough which said loops project. Conductors 243 and 244 are sealedthrough the wall of envelope 201 and gas tight bus-hing seals 245 and246 are l-ikewisevprovided Within them. Conductors 243 and 241constitute the input concentric transmission line and conductors 244 and242 constitute the output concentric transmission line through which theultra high frequency'power is efectively led `from the'tube.

t `It the tube is to be operatedfas an amplier the input line isconnected to the source of signals to be amplified while the output lineis connected to a load. If the tube is to be operated as anoscillatorthe input and output lines are connected together byatransmission line of suitable length, all as is well known to thoseskilled in the art.V

By way of example, there will now be considered the design of a klystronamplifier according to my invention intended to operate on a centimeterwavelength and having prismatic resonant cavities 8 centimeters inheight. Let the letter l represent the height of the cavities, i. e.

width of the electron beam; b their depth in the direction of the beamtrajectories, and 2a the width of their reentrant portions perpendicularto the width of the beam (see Figs. 4 and 5). Let represent the lengthof the gap. With the subscript 1, these quantities refer to the buncher,and with the subscript 2 they refer to the catcher.

The cavity 218 must possess dimensions such that it will oscillate in asystem of standing Waves having a half phase wavelength in directionsparallel to its generators or elements. Since the height is to be 8centimeters, the phase wavelength Agn is to be 16 centimeters and thecutoff wavelength )mi is givenby Consequently het: 12.64 cm.

Fig. 6 is a graphv in which .the quantity if *2b for reentrant prismaticcavities is plotted as a function of the parameter a/b for differentvalues of the parameters The curves drawn in solid lines correspond toCurve 601'` is for If, moreover,

is to be 0.8, then C1=1.5 cm. p The abscissa .4 and the ordinate Sintersect at the point 604 on the curve 602 for which @1 5;-02 andaccordingly 1:02a Cm.

The` cavity 218 is thus completely determined.

In its prismatically reentrant portion traversedrby the beam, the cavity219 must oscillate in a system of standing waves one quarter of a phasewavelength long parallel to the: generators of the cavity. Since itsheight or length `is 8 centimeters, its phase wavelength Mp2 Vwill be 32l. centimeters and it's -cutolf wavelength )tez will be given by M2:10.52 cm. In order to employ for both cavities the same lateral exterior'walls Vand the same walls for the drift space corridor, i, e. vto make2521, 2'2'2, 227 and 228 common to the two cavities, one chooses` Theabscissa t2 and the ordinate 2.1 intersect at the point 605 throughwhich passes the solid line curve 606 corresponding to This gives62:0.85 cm. and the cavity 219 is completely etermined as to itsprismatically reentrant portion.

`The magnitude of the short dimension e for the rectarb gular cavity 230which closes the cavity 219 at its upper Vextremity is chosen so as togive to the cavity 230 a cutoff Wavelength 2e' greater than l()centimeters. For example, e=6 cm; will be a suitable value. The twoportions 219 and 230 of the catcher cavity are coupled by means of thecurved boundary 232. Y

Operationrof my klystron is as follows:

Referring to Figs. 2 and 3, heater 205 raises cathode 208 to atemperature at which it emits electrons. These electrons are acceleratedunder the action of the positive potential applied to electrode 212 intocavities 218 and 219 and pass through the gap between grids 233 and 234.Across this gap, electrons are modified as to velocity by the inputfield in chamber 218 and continue their travel through the field-freecorridor between plates 227 and 22S with the electrons having normal orunaffected speed overtaking previously dispatched slower electrons and,in turn, being overtaken by speeded-up electrons started at a latermoment. ln accordance with classical theory, the proper bunching ofelectrons takes place across gap between grids 235 and 236. Theelectrons accordingly represent a concentration of energy in the saidgap and give up energy to resonator chamber 219 which oscillates with areduced VQ without sacrificing the shunt resistance as set forth above.

InV the foregoing ydescriptive specification I have describcd'aparticular embodiment of the principles of my invention, but theseprinciplesrare capable of application in many alternative forms, whichwill be evident to those skilled in the art. For example, I havedescribed the buncher cavity as resonating upon half a wavelength andVthe catcher cavity as resonating upon a quarter-Waveclosed byconducting material and conforming substantially to a prism whoseprincipal section is a reentrant polygon, a pair of parallelelectron-permeable grids vof similar and equal rectangular shape oneformed in a reentrant face of the buncher cavity and the other formed ina face of said buncher cavity opposite the said reentrant face, saidgrids extending in the direction of the buncher cavity prism elementsover that proportion of the height of the buncher cavity prismrepresented by a simple fraction whose numerator and denominator aresmall integers, an input coupling loop in the buncher cavity locateddistant from one end thereof by a simple fraction of the said prismheight, the numerator and denominator of the said fraction being smallintegers, said numerator being a multiple of two and said denominatorbeing a multiple of four, a catcher cavity substantially enclosed byconducting material and conforming except at `one end substantially to aprism whose principal section is a reentrant polygon, the cross-sectionof said catcher cavity being different from the cross-section of saidbuncher cavity, a pair of electron-permeable grids in opposite faces ofthe prismatic portion of the catcher cavity of substantially the samesize, shape and disposition as the buncher cavity grids, a non-reentrantsupplementary cavity of greater cross section than that of the prismaticportion of the catcher cavity closing one end of the catcher cavity,means to support the buncher and catcher cavities parallel with theirgrids in alignment, means t0 generate an electron beam oftwo-dimensional extension having a width substantially equal to theheight of said grids, means to accelerate said beam through all of saidgrids, an output coupling loop in the catcher cavity located adjacentthe junction between the supplementary cavity and the prismatic portionof the catcher cavity, said catcher cavity having in its prismaticportion such cross section and height that an electromagnetic iield ofthe frequency of a eld which in the buncher cavity will have a phasewave length of whose quarter the height of the buncher cavity is an evenmultiple will in the catcher cavity have in propagation down the catchercavity a phase wave length of whose quarter the prismatic height of thecatcher cavity is an odd multiple.

2. An electron discharge tube of the velocity modulation type includingbuncher and catcher cavities, a cathode and a collector electrode, inputcoupling means linking with the volume of the buncher cavity and outputcoupling means linking with the volume of the catcher cavity, thebuncher cavity conforming substantially to a cylindrical solid, a pairof electron-permeable grids occupying substantially equal areas onopposite faces of the buncher cavity cylinder, said areas having in thedirection of the generators of the buncher cavity cylinder a dimensionsubstantially equal to an even number of quarters of the phase wavelength of a eld of given frequency vibrating in a fundamental mode ofthe buncher cavity cross section, the height of the buncher cavitycylinder being substantially equal to an even number of quarters of thesaid buncher cavity phase wave length, said input coupling means beinglocated in thebuncher cavity adjacent a node of the standing Wavepattern of radiation having said buncher cavity phase wave length, thecatcher cavity including a re-entrant cylindrical cavity closed at oneend by a right section of said catcher cavity cylinder and closed atAthe other end by a non-reentrant supplementary cavity, thecatchercylindrical cavity having such length and cross section thatradiation of the Asaid given frequency vibrating Withinlthe catchercavity according tothe said mode vhas a phase wave length whose quarteris an odd submultiple of the cylindrical catcher cavity length, and saidoutput coupling means being located remote from said one end of thecatcher cylindrical cavity an odd number of quartersof said catchercavity phase Wave length.

3. An electron velocity modulation'discharge device comprising incombination narrow rectangular cathode and collector electrodes,rbuncher vand catcher reentrant prismatic cavity resonators ofsubstantially the same height with each other and with said cathode andcollector electrodes but of different cross sections, said resonatorsbeing adapted to have a. ribbon-shaped electron stream emitted by saidcathode pass through narrow electron permeable sections in saidresonators extending overthe total height thereof, said buncher cavitybeing shortcircuited at both ends and said catcher cavity beingshrtcircuited at one end only, a non-re-entrant supplementary cavitycoupled to the other end of the catcher cavity, the buncher cavity beingadapted to oscillate in a system of standing waves having ahalf-phase-wavelength equal to its height and the catcher cavity beingadapted to oscillate in a system of standing Waves having aquarter-phase wavelength equal to its height, and means for applyinginput energy to the buncher and for extracting output amplified energyfrom the catcher.

4. A velocity modulation electron discharge device comprising incombination narrow rectangular cathode and collector electrodes,ybuncher `and `catcher reentrant prismatic cavity resonators ofdifferent cross sections but of substantially the same height with eachother and with said cathode and collector electrodes and adapted to havea ribbon-shaped electron stream emitted by said cathode pass throughnarrow electron permeable sections extending over the total heightthereof, the buncher resonator being short-circuited at both ends andthe catcher resonator being short-circuited at one endV only, asupplementary cavity resonator coupled to the other end of said catcherresonator, the buncher resonator being adapted to oscillate in a systemof standing waves having a half-phase-wavelength equal to its height andthe catcher resonator being adapted to oscillate in a system of standingwaves having a quarter-phase-Wavelength equal to its height, means forapplying input energy to said buncher resonator located near one endthereof, and means for extracting output amplified energy from thecatcher resonator located near the junction of the catcher andsupplementary resonators.

5. An electron discharge tube comprising two cavity resonators eachconforming at least in part substantially to a cylinder whose principalsection is a plane figure having a re-entrant portion, the principalsections of said two resonators being of unequal areas, each saidresonator having on one of its re-entrant faces and on an exterior facea substantially rectangular electron-permeable grid, all four of saidgrids extending over substantially equal lengths parallel to theelements of the cylinders, the first of said resonators beingshort-circuited at both ends, the second of said resonators beingshort-circuited at one end only, a supplementary cavity resonatorcoupled to the other end of said second cylindrical resonator, saidcylindrical resonators being supported with their cylindrical elementsparallel and with said four grids in line with each other, a cathodeadjacent a first one of said cylindrical resonators adapted to generatea ribbon-shaped electron beam having a width substantially equal to thelength of said grids, and means to accelerate said beam through all ofsaid grids, the first of said cylindrical resonators having a crosssection adapted to provide over the length of said first cylindricalresonator for energy of a frequency at which said first cylindricalresonator resonates a path substantially equal to an even number ofquarters of the phase wave length of such energy in propagationlengthwise of said first cylindrical resonator and said secondcylindrical resonator having a cross section adapted to provide over thelength of said second cylindrical resonator for energy of the saidfrequency a path substantially equal to an odd number of quarters of thephase wave length of such energy in propagation lengthwise of saidsecond cylindrical resonator.

6. An electron discharge tube according to claim including inputcoupling means located distant from one end of the first cylindricalresonator by an even number of quarters of the phase wave length ofenergy of said frequency in propagation lengthwise of said first cylnddrical resonator and including output coupling means located distantfrom said one end of said second cylindrical resonator by an odd numberof quarters of the phase wave length of energy of said frequency inpropagation lengthwise of said second cylindrical resonator.

7. An electron discharge tube comprising two cylindrical cavityresonators of substantially the same height and of diierent re-entrantcross sections, the first of said resonators being short-circuited atboth ends and the second being short-circuited at one end thereof only,a supplementary cavity resonator coupled to the other end of said secondcylindrical resonator, said supplementary cavity having a greater crosssection than said second cylindrical resonator, said cylindricalresonators having each two electron-permeable grids formed in oppositefaces thereof, said grids extending over substantially the total heightof said cylindrical resonators, means sup* porting said cylindricalresonators with their grids in line and parallel to each other, acathode adjacent a first one of said cylindrical resonators adapted togenerate a ribbon-shaped electron beam having a width substantiallyequal to and aligned with the length of said grids, means to acceleratethe beam through all of said grids, means to couple a radio frequencyfield into said first cylindrical resonator, and means located adjacentthe junction between the second cylindrical resonator and thesupplementary resonator to couple out radio frequency energy from. thesecond of said cylindrical resonators. v

8. An electron discharge tube comprising a buncher cavity resonatorconforming at least in part substantially to a prism having lateral, topand bottom walls of conductive material and having a re-entrantcross-section adapted to provide over the length of said buncherresonator between its top and bottom walls for energy of a frequency atwhich said buncher resonator resonates a path substantially equal to aneven number of quarters of the phase wave length of such energy inpropagation lengthwise of said buncher resonator, a catcher cavityresonator conforming at least in part substantially to a prism of thesame length as said buncher resonator, said catcher resonator havinglateral and bottom walls of conductive material and being open-ended atits top and having a re-entrant cross-section adapted to provide overthe length of said catcher resonator for energy of said frequency a pathsubstantially equal to an odd number of quarters of the phase Wavelength of such energy in propagation lengthwise of said catcherresonator, a non-reentrant supplementary cavity resonator, of conductivematerial joined to said catcher resonator at the top thereof, saidsupplementary resonator having a greater crosssection than that of saidcatcher resonator, four electronpermeable grids disposed two on eachofthe buncher and catcher resonators and extending over substantiallythe total lengths of said buncher and catcher resonators parallel totheir prismatic elements, means to support said buncher and catcherresonators with their prism-atie elements parallel and with said fourgrids in line, a cathode adjacent said buncher resonator adapted togenerate a ribbon-shaped electron beam having a width substantiallyequal to the common length of said buncher and catcher resonators, meansto accelerate the electron beam from said cathode through all of saidgrids, means to couple a radio frequency held into said buncherresonator, and means located adjacent the junction between thesupplementary resonator and the catcher resonator to couple out radiofrequency energy from the catcher resonator.

9. An electron discharge tube according to claim 8 in which the means tocouple the radio frequency iield into the buncher resonator is locateddistant from one end of the buncher resonator by an even number ofquarters of the phase wave length of energy of said frequency inpropagation lengthwise of said buncher resonator.

(References on following page) References Cited in the le of this patentUNITED STATES PATENTS Litton Oct. 13, 1942 yLitton Dec. 22, 1942 FremlinNov. 26, 1946 Marsh et al. Mar. 29, 1949 1,2 Woodyard et a1 Apr. 5, 1949Harries Apr. 26, 1949 Law May 24, 1949 Harrison Sept. 27, 1949 SunsteinMay 30, 1950 Bonne et al. Nov. 6, 1951

